What to do with the flower after blooming is complete and drying up?
You can remove the faded flower as described in the following article. This will improve the appearance of the plant and may prevent plant diseases.
https://www.gardeningknowhow.com/ornamental/flowers/bop/deadhead-bird-of-paradise.htm
The only reason to leave the dried flower on would be if you wanted to propagate the plant by collecting seeds for planting.
I have 3 or 4 areas planted with giant white birds as the focal point. One area has 2 stalks that are over 20' tall, which I need to remove or cut back, as I don't want to deal with wind damage from storms (I live in south FL). If I cut the stalk to say 3' or 4' in height, will the stalk regenerate with the plant growing from the remaining stalk or do I need to remove the stalk entirely?
It is best to cut only 1/3 of the plant's size in any one year. If that plant has at least 3 stalks, you could cut one of the stalks to the ground. Otherwise, plan to cut 1/3 off the height each year.
Should I fertilize Bird of Paradise and, if so, what should I use?
This article has some great advice on the best fertilizers for Bird of Paradise:
We have bird of paradise in my front yard and they are beautiful. The issue that we have is they are now 7 feet tall and blocking the view of the house. Can I cut them back, and if so, where do we cut them?
Yes, you can prune back your bird of paradise plant. It is best to remove only 1/3 of the branches or of the height of each branch per year to avoid damaging its health. By pruning over several years, you can reduce the height over time.
https://www.gardeningknowhow.com/ornamental/flowers/bop/bird-of-paradise-pruning.htm
We have 17 Red Mexican Birds of Paradise plants in our Phoenix, AZ yard. They are probably 20 years old. Right now (Late Oct) they are done growing their peas and the leaves are turning yellow. I want to trim them back to the ground because they look ugly right now but my wife says that a frost (we usually get one ore two a year in Feb or so) would kill them. Since they are so old, can I trim them now?
The best time to prune Mexican Bird of Paradise is in late winter or early spring. If they haven't been cut back in years, they can be cut back to near the ground. They can also be pruned annually to improve their shape.
We live in Huntsville, AL, zone 7b. Spring 2015 I purchased this plant clearance at local store. Last winter my husband and I were able to move it from inside our home to our porch pending the weather. The plant is now too big to be kept in our home for the winter so it must stay on our front porch. I am puzzled, for I do not know how to protect it from our chilly nights and intermittently freezing weather. Please help, thank you very much.
The fact that the plant is in a sheltered corner will help. However, this plant is very prone to being damaged by cold. Protecting the roots is the most important for plant survival, but protecting the stem and leaves is also important for the plant's appearance next year. See these articles:
https://www.gardeningknowhow.com/ornamental/flowers/bop/bird-paradise-plant-freeze.htm
https://www.gardeningknowhow.com/special/containers/overwintering-container-plants.htm
https://www.gardeningknowhow.com/plant-problems/environmental/protecting-plants-winter.htm
Pruning the plant back and taking it indoors may also be a possibility:
http://www.south-florida-plant-guide.com/white-bird-of-paradise.html
Will the flower bloom in water if cut from the tree prior to blooming?
Cut the stem of the Bird Of Paradise under warm water at an angle.
Allow the flower to hydrate for a few hours.
To help the flower open you insert your finger into the flower at the stalk end and gently work the flower open out to the end.
Widen the opening enough to see the flowers.
Gently pull the top of the floret and pull it out.
Put the stem back in the water.
Use a floral preservative in the water to extent the life of the cut Bird Of Paradise.